1. Field of the Invention
The present invention relates to a linear guide apparatus having circulating paths for rolling members interposed between a guide rail and a slider movable on the guide rail, and in particular, to a linear guide apparatus having a feeding position for lubricating oil supplied to circulating paths for rolling members.
2. Description of the Relevant Art
A linear guide apparatus of this type is disclosed, for example, in Japanese Utility Model Laid-Open Publication No. 58-155426.
The linear guide apparatus comprises a long guide rail having rolling grooves formed in both sides for balls which are rolling members, and a slider main body mounted on the guide rail in a movable, straddling relationship thereto and having ball rolling grooves respectively corresponding to the ball rolling grooves of the guide rail. The slider main body further has through holes as ball paths extending in the axial direction in parallel to the ball rolling grooves. End caps are respectively fixed to opposite ends of the slider main body, and each of the end caps has a pair of ball circulating paths, having a half-doughnut shape, formed as recesses, respectively extending between the ball rolling grooves of the slider main body and corresponding through holes. An oil feed groove is connected to the ball circulating paths. Balls are inserted rollably in the ball rolling grooves and through holes of the guide rail and the slider main body, and in the half-doughnut shaped ball circulating paths.
When the slider moves relative to the guide rail in the axial direction, the balls roll and circulate through the through holes, the ball circulating paths, and the ball rolling grooves, allowing the slider to move smoothly in the axial direction due to the rolling of the balls. In this case, a lubricant is supplied to the ball circulating paths through the oil feed groove. By virtue of this, the smooth rolling of the balls can be assured.
The lubricant is generally supplied to the oil feed groove through an oil feed member such as an oil feed nipple screwed into a threaded hole formed in the front surface of the end cap. However, when the oil feed nipple located on the front surface of the end cap interferes with a stopper provided at the end of the guide rail, or interferes with a member to be mounted on the slider, the location of the oil feed nipple must be changed to the side of the slider. When such a need occurs, in the prior art, as shown in FIG. 6, a female threaded hole G is formed, by machining, in the side of the slider main body A and at the same time, an oil passage C is formed, by machining, in the slider main body A, which is typically made of metal, so that the female threaded hole G is brought in communication with the oil feed groove of the end cap. For this reason, a problem is involved in that the cost is increased due to the machining, and furthermore, it is difficult to quickly change the location of the grease nipple when such a request occurs. Moreover, since machining is required, metallic chips remaining in the oil passage are apt to be transported into the ball circulating paths together with the lubricant.
As a countermeasure to such a problem, it has been proposed, as shown in FIG. 7, to form oil passages D beforehand at three positions on the front face and side faces of an end cap F manufactured by plastic injection molding, and subsequently closing two of the three oil passages using blind plugs. However, time is required to screw the blind plugs into the oil passages resulting in high costs.